Open the app drawer
Find the app you want
Press and hold the app icon
Drag the icon to the home screen
Release it where you want it placed
If there is no app drawer, open the app list in settings or launcher options
Check home screen settings to make sure apps are allowed to appear
If the app is hidden, unhide it in launcher settings
If the app was removed, reinstall it from the app store
Restart the phone if the app still does not appear